1. Field of the Invention
The present invention relates to improved miter saws for cutting wood and more particularly, it relates to a shutter device in such miter saws which serves to shut the passage of chips severed from a workpiece to thereby increase the safety of cutting operation.
2. Description of Prior Art
Such miter saws may comprise a supporting frame of generally rectangular form, a work fence secured to the frame, and a circular turntable rotatably mounted on the frame and a structure secured to and movable with the turntable. The structure includes a saw blade, a blade guard and a drive motor which are bodily movable along a vertical path relative to the turntable. Thus, such saws can be selectively set for cross-cutting and mitering elongated workpiece upon angular displacement of the saw blade. Such miter saws are also commonly provided with means for shutting the saw blade clearance gap in the fence in order to avoid any possibility of chips passing through the gap into a spacing between the saw blade and the blade guard. However, as the position and the angle at which the saw blade intersects the gap varies with the working angle of the blade, the previous known means has been disadvantageously complicated in construction and especially, it has failed to effectively shut the gap in response to the variable working angle of the blade.
A review of the prior art patents revealed U.S. Pat. Nos. 4,211,134 and 4,452,117 which disclose a saw unit of the radial arm type in which a guide fence is slidably movable upon rotation of a turntable. However, these prior art arrangement, provided for radial arm saws, are complicated in construction, and as the whole guide fence is moved, it tends to jolt, resulting in inacurate cutting operation. Additionally, the arrangements have a disadvantage that the turntable tends to turn heavily.